1. Field of the Invention
The present invention relates to a motor driving control apparatus.
2. Related Background Art
Along with the development of switching technologies in recent years, it has become possible to drive a five-phase stepping motor by chopper driving. There is one chopper method used for the five-phase stepping motor, in which the chopper driving is performed in the PWM cycle in which the current distribution period for switching phases and the holding period of the current are made one cycle, and the current is controlled by controlling the holding period.
Also, there is another method in which the current control is effectuated by controlling the phase switching period Tms. With this method, the Tms period is controlled to become smaller if a motor is driven to rotate at a slower speed with a current that generates an adequate torque.
However, in the former case, if a motor is driven to rotate at a slower speed with a current that generates an adequate torque, the PWM period becomes greater. Then, the PWM frequency presents an audible range, which causes the motor to generate an abnormal sound.
Also, in the latter case, there is a limitation in a clock for generating the Tms period. As a result, the Tms is limited to the minimum period thereof, leading to inadequate current control when a motor is driven to rotate at a slow speed.
The present invention is designed in consideration of the problems discussed above. It is an object of the invention to provide a motor driving control apparatus capable of driving the motor to rotate at low speed with an adequate torque without generating any abnormal sound.
In other words, the present invention provides a motor driving control apparatus which comprises exciting means for supplying current from a power source to a motor coil, first setting means for setting an exciting period to supply current from the power source to the motor coil by the exciting means, second setting means for setting a non-exciting period not to supply current from the power source to the motor coil by the exciting means, and PWM means for repeating alternately the current supply to the motor coil during the exciting period set by the first setting means, and the non-supply of current to the motor coil during the non-exciting period set by the second setting means, and drives the motor by changing the exciting patterns of the exciting means. The motor driving controlling apparatus is further provided with third setting means for setting a short period to enable each of the feeding points of the motor coil to be short-circuited totally during the non-exciting period, and fourth setting means for setting an open period to enable each of the feeding points of the motor coil to be totally in an open status.
Also, the present invention provides a motor driving control apparatus which comprises exciting means for supplying current from a power source to a motor coil, first setting means for setting an exciting period to supply current from the power source to the motor coil by the exciting means, second setting means for setting a non-exciting period not to supply current from the power source to the motor coil by the exciting means, and PWM means for repeating alternately the current supply to the motor coil during the exciting period set by the first setting means, and the non-supply of current to the motor coil during the non-exciting period set by the second setting means, and drives the motor by changing the exciting patterns of the exciting means. The motor driving control apparatus is further provided with third setting means for setting a short period to enable each of the feeding points of the motor coil to be short-circuited totally during the non-exciting period, fourth setting means for setting an open period to enable each of the feeding points of the motor coil to be totally in open status, fifth setting means for setting the value of current flowing in the motor, detecting means for detecting the motor current flowing in the motor, sixth setting means for setting the current target value to make the motor current a desired current value, comparing means for comparing the motor current detected by the detecting means, and the target value set by the sixth setting means, and controlling means for controlling the motor current set by the fifth setting means in accordance with the result of comparison of the comparing means. The fifth setting means is provided with changing means for changing the open period set by the fifth setting means.
These and other objects, features and advantages of the present invention will become more apparent upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.